Method for shearing pipe and providing a compression seal

ABSTRACT

The method of providing blowout preventer shear rams which will shear pipe then provide a face-to-face compression seal comprising providing an upper shear ram having an upper shear ram blade and a pipe lifter, providing a lower shear ram having a lower shear ram blade, and a pipe lifter, providing a face-to-face seal, moving the upper and lower shear rams into the bore towards one another, shearing the pipe in the bore of the blowout preventer, engaging the upper sheared portion of the pipe with the pipe lifters, lifting the upper sheared portion of the pipe with the pipe lifters to a position above the face-to-face seal, engaging the face-to-face compression seal to effect a seal across the bore.

TECHNICAL FIELD

This invention relates to the method of providing shear rams which willshear the pipe and then lift the sheared section of pipe above the shearplane to allow a face-to-face compression seal between the rams.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

REFERENCE TO A “MICROFICHE APPENDIX”

Not applicable

BACKGROUND OF THE INVENTION

Deepwater offshore drilling requires that a vessel at the surface beconnected through a drilling riser and a large blowout preventer stackto the seafloor wellhead. The seafloor wellhead is the structural anchorpiece into the seabed and the basic support for the casing strings whichare placed in the well bore as long tubular pressure vessels. During theprocess of drilling the well, the blowout preventer stack on the top ofthe subsea wellhead provides the second level of pressure control forthe well. The first level being provided by the weighted drilling mudwithin the bore.

During the drilling process, weighted drilling mud circulates down astring of drill pipe to the drilling bit at the bottom of the hole andback up the annular area between the outside diameter of the drill pipeand the inside diameter of the drilled hole or the casing, depending onthe depth.

Coming back up above the blowout preventer stack, the drilling mud willcontinue to travel back outside the drill pipe and inside the drillingriser, which is much large than the casing. The drilling riser has to belarge enough to pass the casing strings run into the well, as well asthe casing hangers which will suspend the casing strings. The bore in acontemporary riser will be at least twenty inches in diameter. Itadditionally has to be pressure competent to handle the pressure of theweighed mud, but does not have the same pressure requirement as theblowout preventer stack itself.

As wells are drilled into progressively deeper and deeper formations,the subsurface pressure and therefore the pressure which the blowoutpreventer stack must be able to withstand becomes greater and greater.This is the same for drilling on the surface of the land and subseadrilling on the surface of the seafloor. Early subsea blowout preventerstacks were of a 5,000 p.s.i. working pressure, and over time theseevolved to 10,000 and 15,000 p.s.i. working pressure. As the workingpressure of components becomes higher, the pressure holding componentsnaturally become both heavier and taller. Additionally, in the higherpressure situations, redundant components have been added, again addingto the height. The 15,000 blowout preventer stacks have become in therange of 800,000 lbs. and 80 feet tall. This provides enormouscomplications on the ability to handle the equipment as well as theloadings on the seafloor wellhead. In addition to the direct weight loadon the subsea wellheads, side angle loadings from the drilling riserwhen the surface vessel drifts off the well centerline are an enormousaddition to the stresses on both the subsea wellhead and the seafloorformations. Similarly pipe sizes and weights have increased as well.

Shear rams within these blowout preventers are utilized to shear pipeonly in emergency cases when there is no other solution to securing asubsea well installation. Securing the well involves both the steps ofshearing the pipe in half and then providing a seal across the wellbore. Ideally a single blowout preventer ram will be equipped with shearrams which upon actuation will shear and seal in a single movement andthen provide a seal which is compression set. Being compression set isbeneficial as the extreme destructive nature of cutting high strengthpipe in half tends to damage any kind of seal, and a compression setseal is the most “self-healing” type of seal. The high pressuresgenerated by being compression set will tend to seal over many defectsin the seal.

It can be sometimes presumed that the sheared section of pipe above theshear ram will be yanked out of the seal area upon shearing if the pipeis in its normal tension is a subsea drilling system. This is not alwaystrue, and was not true in the 2010 Gulf of Mexico Macondo blowout casewhen the incapacitated rig could not pick up anything.

One solution provided for this is to have a seal which seal in the shearplane as a face seal. This seal is dependent upon not scratching theseal or the mating seal surfaces, and that no shrapnel from the shearingoperation gets in the way so it is a less reliable seal.

Another solution which has been provided is to literally bend the pipeout of the way. This has worked on some section of pipe, but withextreme high strength pipe and connections used today, there is greatdifficulty in bending the pipe and coupling sections.

The ideal goal is to simply shear the pipe and have the sheared piecesnot in the way of a face-to-face compression seal.

BRIEF SUMMARY OF THE INVENTION

The object of this invention is to provide blowout preventer shear ramswhich will shear pipe in the bore of the blowout preventer.

A second object of this invention is to provide blowout preventer shearrams which will seal in a face-to-face compression seal.

A third object of this invention is to provide shear rams which willraise the shear section of pipe above the shear plane above the sealingarea.

Another object of this invention is to provide a secondary seal whichwill independently seal across the interface of the shear rams if theprimary seal fails.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a contemporary deep-water riser system.

FIG. 2 is a perspective view of a blowout preventer stack utilizing thefeatures of this invention.

FIG. 3 is a perspective view of a subsea wellhead housing which theblowout preventer stack of this invention would land on.

FIG. 4 is a perspective view of the lower portion of the blowoutpreventer stack of FIG. 2 , generally called the lower BOP stack.

FIG. 5 is a perspective view of the upper portion of the blowoutpreventer stack of FIG. 2 , generally called the lower marine riserpackage or LMRP.

FIG. 6 is a perspective view of a section of the drilling riser whichwill be used to lower the blowout preventer stack.

FIG. 7 is a view of the blowout preventer stack of FIG. 2 , taken alonglines ″7-7.

FIG. 8 is a view of the blowout preventer stack of FIG. 2 , taken alonglines ″8-8.

FIG. 9 is a top view of FIG. 8 .

FIG. 10 is a perspective view of a pair of shear rams spaced apart.

FIG. 11 is a perspective view of the pair of shear rams of FIG. 10 movedcloser together.

FIG. 12 is a perspective view of a lower shear ram with the lifter inthe initial position.

FIG. 13 is a perspective view of a lower shear ram of FIG. 12 with thelifter rotated to a raised position as it would be during operation whenthe sheared pipe is raised.

FIG. 14 shows a cross section view of a shear ram blowout preventer withthe rams in the fully opened condition.

FIG. 15 shows a figure similar to FIG. 14 with the shear rams moved to aposition of having just sheared the pipe.

FIG. 16 shows a figure similar to FIG. 15 with the shear rams moved to aposition closer to one another and having raised the sheared section ofpipe above the level of the seal.

FIG. 17 shows a figure similar to FIG. 16 with the shear rams movedfully into contact and into face-to-face sealing engagement.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1 , a view of a system 20 which might use thepresent invention is shown. It shows a floating vessel 22 on a body ofwater 24 and having a derrick 26. Drill pipe 28, drilling mud system 30,control reel 32, and control cable 34 are shown. A riser system 40including a flex joint 42 is shown. During drilling the drilling mudcirculated from the drilling mud system 30, up the standpipe 44, downthe drill pipe 28, through the drill bit 46, back up through the casingstrings 48 and 50, through the blowout preventer stack 60, up thru theriser system 40, and out the bell nipple at 62 back into the mud system30.

Blowout preventer stack 60 is landed on a subsea wellhead system 64landed on the seafloor 66. The blowout preventer stack 60 includespressurized accumulators 68, kill valves 70, choke valves 72, choke andkill lines 74, choke and kill connectors 76, choke and kill flex means78, and control pods 80.

Referring now to FIG. 2 , the seafloor drilling system 100 comprises alower blowout preventer stack 102, a lower marine riser package 104, adrilling riser joint 106, and control cables 108.

Referring now to FIG. 3 , a subsea wellhead is shown which the seafloordrilling system lands on. It is the unseen upper portion of the subseawellhead system 64 shown in FIG. 1 .

Referring now to FIG. 4 , the lower blowout preventer stack 102comprises a lower structural section 120, vertical support bottle 122,and upper structural section 124, accumulators 126, choke and killvalves 128, blowout preventers 130 and an upper mandrel 132 which willbe the connection point for the lower marine riser package.

Referring now to FIG. 5 the lower marine riser package 104 is showncomprising a lower marine riser package structure 140, an interface 142for a remotely controlled vehicle (ROV), annular blowout preventers 146,choke and kill flex loops 148, a flexible passageway 150, a riserconnector 152, and an upper half of a riser connector 154.

Referring now to FIG. 6 , a drilling riser joint 106 is shown having alower half of a riser connector 160, a upper half of a riser connector154, and buoyancy sections 162.

Referring now to FIG. 7 , is a view of seafloor drilling system 100taken along lines “7-7” of FIG. 1 showing wellhead connector 170, lowermarine riser connector 172, a man 174 for size perspective, and chokeand kill valves 176.

Referring now to FIG. 8 , is a view of seafloor drilling system 100taken along lines “8-8” of FIG. 1 .

Referring now to FIG. 9 , is a top view of seafloor drilling system 100.

Referring now to FIG. 10 which is a perspective view of a pair of shearram of this present invention including lower shear ram 202 and uppershear ram 204. Lower shear ram 202 has lower shear blade 206, lifter208, body 210 and body seal 212. Upper shear ram 204 has upper shearblade 214, lifter 216, body 218, body seal 220, and front seal portion222.

Referring now to FIG. 11 , lower shear ram 202 and upper shear ram 204are moved closer to one another such that the upper shear blade 214 ispassing above lower shear blade 206 as any pipe in the blowout preventerbore is being sheared.

Referring now to FIG. 12 , lower shear ram 202 is shown in greaterdetail. Front portion 230 of body seal 212 is shown, and this is wherethe front face of upper shear blade 214 will contact to seal across thebore of the blowout preventer. It can be noted that the lifter 208remains in the same location as seen in FIGS. 10 and 11 .

Referring now to FIG. 13 , lifter 208 is shown in the rotated positionafter the pipe is sheared and has been lifted.

Referring now to FIG. 14 which shows a shear ram blowout preventer inthe fully opened condition, blowout preventer body 300 is shown having acentral bore 302, ram cavities 304 and 306, and an injection port 308.Upper shear ram 204 has actuating rod 312, body seal 314, upper shearblade 214, pipe lifter 216, front curved surface 320, pivot pin 322, anda rear curved or cylindrical surface 324. Lower shear ram 202 hasactuating rod 332, lower shear blade 206, front seal 336, body seal 212,and pipe lifter 208 with pivot pin 342 and rear curved or cylindricalsurface 344.

Referring now to FIG. 15 which shows upper shear ram 204 and lower shearram 202 moved forward to the point that pipe 350 in the bore as justbeing sheared into upper pipe section 352 and lower sheared section 354and the pipe lifters 208 and 216 are contacting upper pipe section 352.

Referring now to FIG. 16 which shows as the upper shear ram 204 andlower shear ram 202 have continued to move forward to lift upper pipe352 to an elevation above the front seal 336 by pivoting the pipelifters 208 and 216 about pivot pins 322 and 342 and sliding about rearcurved surfaces 324 and 344. The purpose of the rear curved surfaces 324and 344 is to withstand any high loadings in this process as a bearingload rather than a shear load on the pivot pins 322 and 342.

Referring now to FIG. 17 which shows upper shear ram 204 has engaged andsealed with lower shear ram 202 with the front seal 336 sealing againstthe front of upper shear blade 214 at 356. In this way the lower shearedsection 354 remains below the shear and seal plane and the upper shearedsection 352 has been automatically lifted sufficiently to allow aconventional face-to-face seal between the upper and lower shear rams202 and 204. This avoids the conventional problems of having toliterally bend one of the sheared pipe ends out of the way or settlingfor a sliding seal at the shear plane rather than a superiorface-to-face compression set seal. Additionally groove 358 is providedas a passageway for a plastic packing sealant material which can beinjected into the blowout preventer body 300 at the injection port 308seen in FIG. 14 as a secondary seal means if there turns out to be adefect in the primary seal 336. The preferred embodiment describedutilizes pivoting plates to lift the sheared section of pipe to allowthe sealing, however, other motions such as an angled sliding action arealso possible.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope and spirit of the invention.Accordingly, the protection sought herein is as set forth in the claimsbelow.

That which is claimed is:
 1. The method of providing blowout preventer shear rams which will shear pipe in the bore of the blowout preventer and then provide a face-to-face compression seal comprising providing an upper shear ram having an upper shear ram blade and a pipe lifter, providing a lower shear ram having a lower shear ram blade, and a pipe lifter, providing a face-to-face seal on at least one of the upper shear ram or the lower shear ram, placing the upper shear ram and lower shear ram in ram pockets in a blowout preventer on opposite sides of the bore of the blowout preventer, the pipe lifters being in an initial position, moving the upper and lower shear rams into the bore towards one another, shearing the pipe in the bore of the blowout preventer into an upper sheared portion and a lower sheared portion, engaging the upper sheared portion of the pipe with the pipe lifters, lifting the upper sheared portion of the pipe with the pipe lifters to a position above the face-to-face seal, engaging the face-to-face compression seal to effect a seal across the bore.
 2. The method of claim 1, further comprising the face-to-face compression seal engages at least one of the upper shear ram or the lower shear ram blade.
 3. The method of claim 1, further comprising the pipe lifters are pivoted.
 4. The method of claim 3, further comprising the pipe lifters are pivoted on an axle, the shear ram bodies are provided with a body cylindrical surface, the pipe lifters are provided with a lifter cylindrical surface about the axle, the loading from the lifting of the upper sheared pipe section is supported by the lifter cylindrical surface loading against the body cylindrical surface.
 5. The method of claim 1, further comprising the initial contact between the lifters and the pipe to be sheared is above the pivot point of the lifters.
 6. The method of claim 1, further comprising when the shear rams no longer are in contact with the sheared pipe, the lifters will return to the initial position by force of gravity.
 7. The method of claim 1, further comprising when the shear rams no longer are in contact with the sheared pipe and the lifters do not return to the initial position by force of gravity, the lifters will engage the blowout preventer body upon returning to the pockets in a blowout preventer on opposite sides of the bore of the blowout preventer and be forced to return to the initial position.
 8. The method of claim 1, further comprising porting is provided across the face of at one of the shear rams and porting is placed in the blowout preventer body to allow sealant to be pumped across the face of the shear rams to seal when the face-to-face compression seal does not seal. 